Bract in Plants Structure Types and Functions

Bract can be described as the accessory structures that are associated with flowers. These can be defined as the modification of the leaves. Bracts are generally associated with the flower, their anatomical positioning is just below the flower base. There are various types of bract plant structures found in the plant kingdom.

The main role of the bract plant structure is to attract pollinators to increase pollination. This article focuses on the understanding of the bract, bract variants, and role of the bract plant structure in pollination and the difference between bract and bracteole.

Bract Structure

Bracts can be defined as the appendages that are associated with the flower. They are generally located just below the flower. They are the modification of the leaves, they are generally different from the normal leaves present in the plant structure, that is they are different from the foliage leaf. 

They are often associated with the inflorescence axis; they are also evidently attached to the cone scale of a plant. The bract plant structure is generally different from the foliage leaf in the texture structure and color. The bract plant structure is generally shorter in comparison with the regular leaves.

Bracts are generally made up of the phyllopodium or a small part of the phyllopodium. A phyllopodium is an undifferentiated state of the leaf, this is also referred to as the primordial leaf axis. In common terms, it can be described as the expanded base of the leaf and sometimes the stem.

Another characteristic feature of this structure is the vibrant color. Although it does not hold true for all the plants, the majority of the plant bracts are vibrantly coloured. This vibrant color provides an outstanding reproductive advantage to the plants as they increase the chances of pollination. 

The plants that are associated with the bract are known as the bracteate. The other commonly known name for such a plant is bracteolate. The plants that are not associated with any kind of bract structure are known as the ebracteate plants. They are more commonly referred to as the ebracteolate.

(Images will Be Uploaded Soon)

Bract Variants

There are various variants of the bract plant structure. All the different variations of the bract are associated with the inflorescence have their specific importance. It is important to note that many planets have bract during their early developmental stage but they soon fall or degrade from the plant. 

This phenomenon is mainly observed in deciduous plants. The plant that retains the bract is known as the bracteate plant. In such a plant the bract plant structure helps in the protection of the bud from a very early stage. There are various variants in the bract structure, some of the variants are as follows:

1. Leafy or Foliaceous Bract 

2.  Petaloid Bract 

3.  Spathe Bract 

4.  Involucral Bract

5.  Scaly Bract 

6.  Cupule 

7. Epicalyx 

8. Glume 

9.  Lemma and Palea.

Leafy Bract- These bracts are often known as the foliaceous bract. In these types of the bract structure, the bract usually resembles the leaf of the plant. The leaf is also called foliage thus giving it the name as a foliaceous bract. The example of this bract is seen in the following cases, china-rose whose scientific name is Hibiscus rosa sinensis, Acalypha indica is also known as the Euphorbiaceae, Adhatoda zeylanica (Acanthaceae), and Gynandropsis (Capparidaceae), etc.

Petaloid Bract- These bracts are generally disguised as the petals of the flowers. These petaloids are generally very bright and colorful, the reason behind such appearance can be attributed to the role they perform. This plant bract structure helps in attracting pollinators. Pollinators are the organism that acts as the vector which carries pollen during pollination. There are various examples of petaloid bract which are arranged in the whorl some of the examples include:

1. Bougainvillea spectabilis of Nyctaginaceae, the bracts present here are of bright red color. This allows the bract to attract various pollinators.

2. Poinsettia pulcherrima of Euphorbiaceae, also commonly known as the euphorbia, is the bract that is of bright orange color. The important point to note is that even though it belongs to the petaloid brant structure the bracts of this plant have a leafy structure. 

3. Cornus sp. of Cornaceae family, more commonly known as the dogwood has white coloured bract. These bracts are placed around the flower of the plant providing it with the protective layer. These bracts are arranged like whorls of petals thus closely resembling the petals of the flower.

Spathe Bract- These are the bract structure that is responsible for providing protection to the inflorescence. They are generally thick and long and cover the complete inflorescence of the plant. Some of the more commonly found plant bract structures of this kind are bright yellow or green in color. 

Spathellae is the name given to the variation of this bract structure, it can be defined as the bract which is present where the spadix is branched, and each of the distinct branches of the spadix is covered by a distinct bract structure.

The common example of apathy bract includes the bract structure of the arum, maize, banana and, the spike of Polyanthus.

Involucral Bract- These are the bracts that are found in the Compositae family, here the bracts from the whorls just below the inflorescence. Some time the bract develops a cup shape structure, this arises due to the fusion of different bract. The bract here are green in color, they share some similarity in resemblance with the spathe bract. Another example of a family that has this type of bract includes family Umbelli­ferae, this family includes carrots, which possess the involucral bract.

Scaly Bract- These bracts have a rough and bumpy outer surface. These types of bract include the florets of catkin and cyathium inflorescences. Another common example where this type of scaly bracts is found is a hop, scientific name Humulus lupulus. It is widely used in manufacturing beer, it provides the aroma and taste to the alcoholic beverage.

Cupule- They are the hard woody bract structure found just below the flower, as the flower matures the bracts generally fuse with each other forming a cup-like structure. It covers the base of the fruit. The common example of this type of bract plant structure is seen in the oak, birch, and hazelnuts

Epicalyx- These are some of the most important plant bract structures found in nature. These are the whorls found around the calyx. They are often considered as the modification of the bracteole. Each individual appendage of this bract structure is called an episepal. This is because they closely resemble the sepal found in the plants. The common example of plants that has this epicalyx bract includes families such as  Malvaceae, which includes hibiscus and, Fragaria, which includes strawberries. 

Glume- These are closely related to scaly bract, a common example includes family Gramineae

Lemma and Palea- These are generally found in the family Gramineae, the bract structure is the lemma and a flower-like structure that actually fits inside the bract is called palea, which is the bracteole of the plant

There are various differences between these two plant structures. Some of them are listed below.

Difference Between Bract and Bracteole

Conclusion

Isn't it true that plants are simple? Isn't it true that if it's green, it's a leaf, and if it's not green, it's a flower? Not at all. There's another element of the plant that you don't hear much about, somewhere between a leaf and a flower. It's called a bract, and even if you don't know what it's called, you've probably seen it. Continue reading to find out more about plant bracts. Learn its different variants with examples to develop your conceptual foundation.